An electric motor usually comprises a stator and a rotor rotatable relative to the stator. The stator usually comprises a round stator housing and a plurality of arc magnets installed on the inner surface of the stator housing. The magnets are usually adhered to the stator housing via glue, which is complicated and time-consuming especially when the motor has a lot of magnets. Furthermore, when the motor operates at a high temperature for a long time, the glue is subject to faster aging and the magnets may detach from the stator housing.